Clots are incubated for 2-48 hours, and their degradation is monitored by measuring proteolytic breakdown products in the serum. We have found that fingerstick clots lyse significantly faster than clots of venipuncture blood. We have assayed fingerstick and venipuncture samples for all the proteins known to be involved in fibrinolysis but have not found significant differences between the two. With the hypothesis that matrix metalloproteinases (MMPs) might be contributing to the lysis of fingerstick clots, we assayed fingerstick and venipuncture serum for several MMPs and found that levels of MMP-9 were significantly greater in fingerstick samples. When MMP-9 was added to fingerstick or venipuncture blood, fibrinolysis was accelerated. Therefore, we are hypothesizing that MMP-9 accounts for the greater rate of fibrinolysis observed in fingerstick blood.